Whether you live in a hot, dry climate or a more dewy location, as summer gets going, the weather can begin to feel downright oppressive. Heat and humidity are more than just nuisances for runners, though—they can be dangerous.
According to a six-year study published in the Journal of the American College of Cardiology, heat stroke is the most common cause of sudden death among runners, eclipsing non-heat-related heart attack.
Fortunately, heat- and hydration-related injuries are fairly easy to avoid. By following these tips, you can beat the heat and run safely all summer long.
Hydration: Not Too Little and Not Too Much
Being adequately hydrated before you head out on a run is especially important on hot, humid days, when you are likely to lose a lot of fluid through sweating. In its latest position paper on hydration and exercise, the American College of Sports Medicine stresses that rates of fluid loss, electrolyte balance and tolerance for fluid consumption varies widely among individuals, but the general goal is to never lose more than 2 percent of your bodyweight from fluid during exercise. This can be tough if you normally run first thing in the morning when you're already slightly dehydrated; so it's a good idea to start sipping water as soon as you wake up.
Drinking too much plain water can also be a problem, leading to a condition called hyponatremia, which occurs when you take in so much water that it dilutes the electrolyte levels in your bloodstream to dangerous levels. This normally happens in cooler conditions during long races, when runners stop and drink water at every fluid station despite the fact that they aren't sweating that much. Commercially available sports drinks are formulated to replace both the fluid and the electrolytes lost during exercise, but they can be high in calories and sugar and are normally only necessary during or after longer runs.
To avoid the negative effects of either dehydration or hyponatremia, simply pay attention to your body's natural signals and drink when you feel thirsty. When you're heading out on a warm day, just remember that it's always better to have fluid with you and not need it than to need it and not have it.